<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <link rel="stylesheet" href="./css/颜色.css">
        <title>Document</title>
    </head>
    <body>
        <div id="div1">
            opacity
            元素透明
        </div>
        <div id="div2">
            直渐变色
        </div>
        <div id="div3"></div>
        <div id="div4"></div>
        <div id="div5"></div>
    </body>
</html>